The invention relates to a system for producing semiconductor layer structures by way of epitaxial growth.
It is known to produce semiconductor devices consisting of several layers, by way of epitaxial growth. A substrate in the form of a thin semiconductor crystal platelet--usually referred to as a wafer--is acted upon, in a crucible, by an undercooled or supersaturated molten solution of another semiconductor material. The atoms of the coating substance which settle out of the solution deposit on the surface of the substrate and form thereon a thin monocrystalline layer which may have a small number of lattice defects and, consequently, good physical properties. This conventional process which, within the English language community, is referred to as the LPE (liquid phase epitaxy) process is used, for example, to produce quaternary mixed-crystal layer structures for use with electro-optical devices. As examples of such devices, there are lasers, LEDs and photodetectors on the basis of gallium-indium-arsenide-phosphide (Ga-In-As-P).
Conventional systems of the type mentioned hereinbefore (Journal of Crystal Growth 46 (1979) pp. 253 to 261; British Telecom Technology Journal Vol. 1 No. 1, July 1983, pp. 23 to 30) are provided with reaction spaces which are accessible from one side and which, in their insides, contain epitaxy crucibles in the form of a so-called multi-chamber sliding boat. In the lower part thereof, there is contained the uncoated substrate, and the upper part comprises several chambers containing the portioned solutions of the required coating substances. The upper part is pushed over the lower part, with the contents of the individual chambers remaining over the substrate for the respectively required periods of time. Crucibles are also known, from the chamber contents of which, with the aid of a slider, each time one solution portion can be separated, which is then sufficient for coating a wafer (Journal of Crystal Growth 60 (1982), pp. 421 to 433). For removing the used up solution, however, the crucible has to be removed from the reaction space. For this purpose, the furnace must each time be cooled and thereafter heated up again. This results in long idle times for the system and also in heat-energy losses.